Rear Sub-Frame Segmentation for Collision Load Management
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Solution Overview
Problem
Existing vehicle body rear part structures struggle to effectively absorb and manage rear collision loads, particularly when there is insufficient collision stroke portion between the rear sub-frame and the rear fastening section, and fail to adequately protect the filler pipe from rear collision loads.
Innovation Solution
A vehicle body rear part structure featuring a pair of rear side frames with curved sections, a rear sub-frame with longitudinal members and a lateral member positioned at intermediate portions of bent sections, and connecting members that divide the frame into protection and deformation sections, allowing for improved impact absorption and protection of the filler pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the vehicle body is designed with sufficient collision stroke portion from the rear end to the rear fastening section, then the absorption of rear collision load is improved, but the overall vehicle length increases
Solution Approach 1:
The rear sub-frame is divided into a protection section (from front fastening section to connecting member) and a deformation section (from connecting member to rear fastening section). This segmentation allows different portions to serve different functions: the protection section maintains structural integrity to protect the filler pipe, while the deformation section absorbs collision energy through controlled deformation, achieving both goals without increasing overall vehicle length.
Solution Approach 2:
Different sections of the rear sub-frame are designed with different structural properties. The protection section has higher strength and rigidity to prevent filler pipe damage, while the deformation section is designed with lower strength to allow energy-absorbing deformation. This local differentiation of structural quality enables simultaneous achievement of energy absorption and component protection within compact space.
2Reliability
If the filler pipe is positioned in the crush preventing portion between the rear fastening section and the front fastening section, then the filler pipe is protected from rear collision loads, but the collision stroke portion becomes insufficient
Solution Approach 1:
The rear sub-frame is segmented into protection section and deformation section, with the filler pipe positioned in the protection section. This segmentation allows the filler pipe to be protected from direct collision forces while the deformation section behind it absorbs the collision energy, resolving the contradiction between component protection and energy absorption capacity.
Solution Approach 2:
The deformation section acts as an intermediary between the collision load and the filler pipe. It is designed to deform and absorb energy before the force reaches the filler pipe, serving as a protective buffer that allows both adequate collision stroke and filler pipe protection within the same space.
3Reliability
If the rear sub-frame is designed with high strength and rigidity to protect the filler pipe, then the filler pipe protection is improved, but the absorption of rear collision load deteriorates
Solution Approach 1:
The rear sub-frame employs local quality differentiation where the protection section has high strength and rigidity for filler pipe protection, while the deformation section has lower strength designed for energy absorption through deformation. This spatial variation in structural properties resolves the contradiction between protection and energy absorption.
Solution Approach 2:
The structure is divided into functional segments with different mechanical properties. The protection section maintains high strength to protect the filler pipe, while the deformation section is designed with controlled lower strength to absorb collision energy, allowing both requirements to be met simultaneously through functional segmentation.
4Loss of energy
If the collision stroke portion is extended to improve energy absorption, then the absorption of rear collision load is improved, but the space available for other components is reduced
Solution Approach 1:
The rear sub-frame is segmented into protection section and deformation section, allowing the deformation section to be optimized for energy absorption while the protection section maintains compact dimensions to preserve space for components like the filler pipe and battery, achieving both energy absorption and space efficiency.
Solution Approach 2:
Different sections are designed with different structural qualities: the deformation section uses lower strength materials or designs that maximize energy absorption per unit volume, while the protection section uses higher strength materials to provide adequate protection in a compact form, optimizing both energy absorption and space utilization.
Data Source
AI summary
A structure for a rear part of a vehicle body includes a rear sub-frame supported by rear side frames. The rear sub-frame includes left and right longitudinal members, and a front lateral member mounted across the left and right longitudinal members. The left and right longitudinal members each have front and rear fastening sections fastened to each of a pair of left and right rear side frames, and left and right bent sections each bent inward in the vehicle width direction between the front and rear fastening sections. The front lateral member is positioned relative to the left and right longitudinal members at the intermediate portions of the left and right bent sections. The intermediate portions of the left and right bent sections are joined to the pair of rear side frames while the left and right longitudinal members are held by the lateral member.